At room temperature, acetaldehyde (H3CC(O)H) is more stable than vinyl alcohol (H2C=CHOH) by 42.7 kJ/mol:[1]

H2C=CHOH → H3CC(O)H ΔH298,g = −42.7 kJ/mol

The uncatalyzed keto-enol tautomerization by a 1,3-hydrogen migration is forbidden by the Woodward-Hoffmann rules and therefore has a high activation barrier and is not a significant pathway at or near room temperature. However, even trace amounts of acids or bases (including water) can catalyze the reaction. Even with rigorous precautions to minimize adventitious moisture or proton sources, vinyl alcohol can only be stored for minutes to hours before isomerizing to acetaldehyde. (Carbonic acid is another example of a substance that is kinetically stable when rigorously pure, but decomposes rapidly due to catalysis by trace moisture.)

The tautomerization can also be catalyzed via photochemical process. These findings suggest that the keto-enol tautomerization is a viable route under atmospheric and stratospheric conditions, relevant to a role for vinyl alcohol in the production of organic acids in the atmosphere.[2][3]